The present invention relates to a silver halide photographic photosensitive material and a method for forming superhigh contrast negative images using the photosensitive material, and in particular to a silver halide photographic photosensitive material used for photomechanical process.
In the field of graphic arts, image forming systems which can provide photographic characteristics of superhigh contrast (especially, at least 10 in gamma value) are necessary to make it possible to perform good reproduction of line images or continuous tone images comprising dot images. For obtaining photographic characteristics of high contrast using stable developers, use of hydrazine derivatives has been known as described in U.S. Pat. Nos.4,166,742, 4,168,977, 4,211,857, 4,224,401, 4,311,781 and 4,272,606. According to these methods, photographic characteristics of superhigh contrast and high sensitivity can be obtained and furthermore, developers can contain sulfites in a high concentration. Therefore, stability of developers against oxidation with air is markedly higher than lith developers. However, it is known that conventional hydrazine compounds have some defects. Thus, it has been attempted to make the conventional hydrazine compounds have an undiffusible structure for the purpose of diminishing adverse effects on other photographic photosensitive materials owing to their flowing out into developers. Such undiffusible hydrazine compounds are needed to be used in a large amount for sensitization and enhancement of contrast and as a result, physical strength of the resulting photosensitive layer is deteriorated or the hydrazine compounds precipitate in the coating solutions. Moreover, when the photosensitive materials are processed with exhausted developers which have been used for processing of a lot of photosensitive materials, sufficiently high contrast cannot be obtained. Furthermore, since the superhigh contrast systems using hydrazine compounds require developers of relatively high pH, for example, 11.5 or 11.8, there are problems such as high dangerousness in handling and large BOD and COD in disposal of waste solutions. In addition, since the pH buffers for keeping constant the pH of developers must be used in a large amount, solid concentration of developers increases and the developers become viscous, and the scattered developers are difficult to wipe off. Thus, development of hydrazine. compounds which can provide high contrast using developers of lower pH has been desired. Furthermore, in general, reversal photosensitive materials handled under roomlight occupy a large field as one of photomechanical photosensitive materials, and in this field, demanded is a high extractability of letters enough to be able to reproduce even the fine Ming letters. For this purpose, development of nucleating agents higher in activity has been demanded. Especially, for roomlight photosensitive materials of low sensitivity capable of being handled even under roomlight, development of nucleating agents which hardly cause increase of contrast and have higher activity has been desired.